The present invention relates to a universal beam for supporting a movable load, the manufacture of which includes extrusion, said beam having a substantially symmetrical U-shaped profile, between the shanks of which is a connecting member and below that a space for means to support, guide and drive the load, the height and width of the beam being approximately equal and its corners being provided with thicker portions for attachment.
The object of the invention is to provide a beam of extrudable material which can be used for many advanced applications, the multiplicity of applications being enabled by designing a beam that, thanks to its low weight, is easily manageable and inexpensive even in considerable lengths and long tracks, which is easy to assemble and gives a rigid, strong attachment that, despite its low weight enables precision handling of loads with maximum weight and acceleration in the most varying kinds of loading, that suits widely differing drive systems, that permits the load to be moved and controlled quietly and that also fulfils strict hygienic demands. The beam is primarily designed for robots and other load handlers with payloads that are moved in different dimensions, at least one of which is a linear dimension.
As far as is known no beam exists that comes close to fulfilling all these requirements. The beams coming closest are all made from extruded aluminium alloys. However, they have all been developed for specific applications and it is therefore natural that they do not have the properties described above qualifying them to be termed universal beams. The beam shown in German patent specification 3 336 496, for instance, permits quiet and rapid load transfer but is not a universal beam. In relation to its weight, it exhibits poor rigidity when loaded transversely to its longitudinal axis and its torsional stiffness is extremely poor which means, for instance, that two parallel beams must be used where a single universal beam according to the present invention would suffice. It is also heavy and cumbersome to handle and assemble. It requires expensive external arrangements for its attachment, and rigid intermediate supports arranged at short intervals if appreciable rigidity and bearing capacity are to be achieved.
Said limitations also apply to an even greater extent to the beam shown in Swedish patent specification 449,200. This beam is totally incapable of handling loads during acceleration that produces torsional moment about the longitudinal axis of the beam for the simple reason that trucks that can be built into the beam are quite incapable of transmitting such torsional moment.
There are also several beams and linear systems that include an extruded aluminium profile whose width and height differ greatly. Such a profile cannot fall under the concept universal beam since it only has satisfactory flexural rigidity in one direction and its torsional stiffness is poor in relation to its weight. Furthermore, without external arrangements, it is not suitable for applications requiring good hygiene, nor where quiet running is a requirement.
Finally, there are examples of beam profiles with satisfactory flexural rigidity in all directions and satisfactory torsional stiffness, but they are not arranged to permit the use of quietly moving trucks. The user must insert special linear elements with tracks for balls or rollers. Such elements cause disturbing noise and are sensitive to tough environments. They are also expensive. The user of such beam profiles must also rely on belt transmission, thereby limiting application to relatively short tracks. Thus such beam profiles also fail to qualify for the term of universal beam.
The universal beam for movable loads according to the invention is manufactured primarily by means of extrusion. It has a substantially symmetrical, U-shaped profile, between the shanks of which is a connecting member and an open space for means to support, guide and drive the load. When the U-shaped profile is oriented with vertical axis of symmetry and its open portion facing downwards, the space for said means is arranged below the connecting member. The height of the profile is equal to or slightly greater than its width. Its corners are provided with thickened portions for attachment.
The universal beam is characterized in that the connecting member is arranged between locally reinforced portions of the shanks of the profile and that the U-shaped profile above the reinforced portions, except in the corners, has a thickness that is at most 5% of the width of the beam. The connecting member consists of two drums joined by a central, substantially horizontal transverse wall. The outer wall of the drums consists of said locally reinforced portions, their bottom wall being shaped with a widened, for the most part horizontal and flat lower side, while their inner wall is formed with a rigid attachment to the central transverse wall and under there with a substantially vertical, flat surface.
In a preferred embodiment the extension of the substantially vertical, flat surfaces is less than the extension of the lower side of the lower walls of the drums.
In a preferred embodiment the thickness of the U-shaped profile above the reinforced portions, except in the corners, is at most 4% of the width of the beam.
In a preferred embodiment the length of the transverse wall is greater than the extension of the vertical, flat part of the inner wall of the drums.
In a preferred embodiment the transverse wall connects directly to the upper wall of each drum.
In a preferred embodiment the drums and transverse wall are located at such a height that the section factor of torsional stiffness of the universal beam is at least 30% of the smallest of the two moments of inertia of the beam profile about its main axes of inertia.
In a preferred embodiment the lower, free parts of the shanks are given greater flexural rigidity than the part of the U-shaped profile located above the reinforced portions, with the exception of the corners. In such an embodiment the free parts of the beam shanks are provided with a closed recess that is oblong in the vertical direction.
In a preferred embodiment the lower, thickened corner portions of the beam are also widened so that they extend horizontally inwards towards the plane of mirror symmetry of the beam profile.
In an embodiment particularly suitable for large beams, the closed space of the beam between the upper part of the U-shaped profile and its connecting member is stayed like a truss construction by one or more thin, straight walls. In a preferred such embodiment a thin wall inside the profile, which connects to a thickened portion in the upper corner of the profile or to a locally reinforced portion of a shank, has greater thickness in the vicinity of said connecting points than elsewhere. In an embodiment with walls forming trusses, these are so arranged that a centrally situated space above the connecting member has a width that is at least one third of the width of the beam, thereby providing a return path inside the beam and above the connecting member, for a transmission belt of sufficient width and strength to handle such a large load that the beam can otherwise support.
In a preferred embodiment six substantially flat guiding and supporting surfaces are provided for the movable load, two of which are arranged on the sides of the drums facing each other, two on the lower sides of the drums and two on the upper side of the lower, inwardly widened, thickened corner portions of the beam.
In a preferred embodiment the inwardly facing part of the lower, widened corner portions of the beam is formed with recesses to retain exchangeable strips designed for guiding and sealing against a transmission belt adapted for the system in question for driving the movable load. In a similarly preferred embodiment a long, narrow space is provided between the drums and immediately below the central transverse wall, designed for a friction plate, a rack or other aid for driving the movable load, and by arrangements to guide and secure these aids.
In another preferred embodiment, where attachment of the beam itself is enabled by T-grooves having supporting bosses, such grooves are arranged in said locally reinforced portions, the upper and lower supporting bosses of said grooves being in direct and close connection to the upper or lower wall respectively, of the adjacent drum. In another embodiment of the beam, the manufacture of which includes extrusion, attachment grooves are shaped with a pronounced bevel at the opening towards the outer side of the beam, and in its inner part with a lateral space of a size adapted to receive threaded square washers, other nuts and flat pieces of steel with threaded openings and the like for insertion obliquely from the side into the groove, without requiring access to the ends of the beam.
The invention also relates to a tool for extruding beams or beam halves, etc. in accordance with the above. Characteristic of the tool is that the part of the tool where the extruded beam leaves the tool has an extrusion gap shaped substantially in accordance with the beam profile described above. Particularly large profiles and long beams are produced by welding together two identical, extruded beam halves using longitudinally running welds, one of which is located centrally in the upper part of the U-shaped profile and the other centrally in the transverse wall of the connecting member.
The need fulfilled by the present invention has long been known without being satisfied. The need is to provide a universal beam that can be used independently and as a component in a building box system for a plurality of advanced applications. Some examples are:
Linear and surface portal robots with high precision, large span and considerable loading with weight or acceleration of considerable mass. PA1 Pillar robots with high precision, great difference in height, large load and great acceleration both vertically and horizontally. PA1 Shuttles, conveyors for great load and acceleration. PA1 Vertical robots, e.g. in installations for high-speed painting of large surfaces. PA1 Programmable automatic overhead cranes with large span and load. PA1 Servo-controlled washing installations, e.g. for aircraft. PA1 Existing profiles cannot handle heavy loads. PA1 Profiles have sometimes had to be rejected due to poor possibility of attachment. PA1 Most of the profiles currently available are excluded from many applications due to their extremely poor torsional stiffness. It is impossible even to hang a cable rack along the side of a beam without the beam becoming extremely twisted.
Insofar as these and similar machines have been possible to build, this has been done mainly with steel constructions. These have been heavy and difficult to handle, as well as being extremely expensive due to their being individually designed and also requiring a considerable amount of welding. Lack of precision in the tracks of the beams has had to be compensated by welding on material which must then be ground or finished in some other way. Poor torsional stiffness in the beams has resulted in poor function or necessitated subsequent reinforcement with extra torsionally rigid drums or trusses. Aluminium profiles with good accuracy and with strength and rigidity suitable for some loads are also in use, as mentioned above. In spite of the relatively large amount of material required, such profiles are too weak to be suitable for most of the applications listed above for the universal beam according to the invention.
Torsionally rigid profiles that are supplemented by linear units to support and guide the load which must transmit considerable moment, have had to be combined from several parts where each part has its own specific function. They have therefore become expensive and sensitive to dirt, as well as being noisy when in operation.
The invention provides a beam that fulfils all the technical requirements in the example applications above, that permits the use of many alternatives for driving carriages or trolleys as well as perfectly acceptable guidance of these even under the influence of considerable forces transverse to the beam and great moment in optional direction. Compared with a somewhat heavier steel beam of the type now used, the beam according to the invention carries several times as much load and also has 100 times greater torsional stiffness. Compared with somewhat heavier aluminium profiles according to current technology, the beam according to the invention has more than equal carrying capacity and permits the handling of loads causing several times greater torsional moment. The beam fulfils high demands for hygiene and has an attractive and functional appearance irrespective of how it is oriented in a room or from which direction it is beheld. It allows quiet movement of the load.